Rings in the Planetesimal Disk of β Pictoris

The nearby main-sequence star β Pictoris is surrounded by an edge-on disk of dust produced by the collisional erosion of larger planetesimals. Here we report the discovery of substructure within the northeast extension of the disk midplane that may represent an asymmetric ring system around β Pic. We present a dynamical model showing that a close stellar flyby with a quiescent disk of planetesimals can create such rings, along with previously unexplained disk asymmetries. Thus we infer that β Pic's planetesimal disk was highly disrupted by a stellar encounter in the last hundred thousand years.